{
  "bibcode": "2005GCN..3110....1C",
  "body": "B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS\nconsortium, report:\n\nUsing the ANDICAM instrument on the 1.3m telescope at CTIO, we\nobtained additional optical/IR imaging of the reported optical afterglow\ncandidate (GCN 3100, Kelson & Berger) of GRB 050315\n(GCN 3094, Parsons et al.) beginning ~35.6 hours post-burst.\nTotal summed exposure times amounted to 10 minutes R and I and\n12.5 minutes in J.\n\nThe source identified as the afterglow candidate has dimmed\nsince our previous observations (GCN 3104, Cobb & Bailyn).\nPreliminary comparison with Landolt Standards PG 1047+003 and RU 149\nyields the following approximate afterglow magnitudes:\n\n        R = 21.6\n        I = 21.5\n\nThe counterpart was again not detected in the IR, with a\nmagnitude limit of J > 18.6.\n\nOur R and I observations are summarized below:\n\n        time post-burst:        R magnitude:    I magnitude:\n        11.6 hours              20.9            20.3\n        35.6 hours              21.6            21.5\n\nWe note that the I-band observations are close to the detection\nlimit, and have measurement errors of >0.2 magnitudes, so the\nevidence for a color change should be treated with caution.\n\nThe R-band magnitudes have errors of ~0.2, so assuming\na power-law afterglow decay (afterglow flux proportional to\nt^alpha), then this corresponds to an alpha of -0.57 +\\- 0.25.",
  "circularId": 3110,
  "createdOn": 1111093487000,
  "email": "cobb@astro.yale.edu",
  "subject": "GRB 050315, SMARTS optical afterglow decay",
  "submitter": "Bethany Cobb at Yale U  <cobb@astro.yale.edu>",
  "eventId": "GRB 050315"
}